Wireless communication systems are in rapid development and, particularly, in recent years, are being developed in a form of supporting a high-speed large-capacity data service in order to satisfy users' various desires. As one way for the high-speed large-capacity data service, installing a small cell as well as an existing macro cell is being taken into consideration.
Commonly, the small cell is installed at a higher frequency band than the macro cell and thus can support a higher data rate than the macro cell. Particularly, in case that the existing macro cell is difficult to support a new service, the small cell supporting the higher data rate is used to support the new service, whereby effective network operation is possible.
In case that the macro cell and the small cell are installed together, it is common that a terminal is serviced only in one cell among the macro cell or the small cell. Hence, further, being serviced from the two cells after forming a connectivity, i.e., a dual connectivity in all of the macro cell and the small cell is being taken into consideration.